Chicago citation style:

APA citation style:

U.S. Congress. (1925) United States Code: Assistant Postmasters, and Clerks and Employees, 39 U.S.C. §§ 81-135. [Periodical] Retrieved from the Library of Congress, https://0-www.loc.gov.oasys.lib.oxy.edu/item/uscode1925-001039003/.

MLA citation style:

U.S. Congress. United States Code: Assistant Postmasters, and Clerks and Employees, 39 U.S.C. §§ 81-135. 1925. Periodical. Retrieved from the Library of Congress, <www.loc.gov/item/uscode1925-001039003/>.